Catalyst for selective hydrogenation of dinitriles

ABSTRACT

Provided is a selective hydrogenation process for producing aminonitriles by contacting the corresponding dinitriles with a hydrogen-containing fluid in the presence of a hydrogenation catalyst, a solvent and a fluoride additive.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 from U.S.Provisional Application Ser. No. 60/168,035 (filed Nov. 30, 1999), whichis incorporated by reference herein as if fully set forth.

FIELD OF THE INVENTION

The invention relates to a selective hydrogenation process for producingaminonitriles in the presence of a fluoride additive.

BACKGROUND OF THE INVENTION

Aminonitriles are a class of important chemicals that have a variety ofindustrial applications. For example, aminonitriles can be used asmonomers for producing high molecular weight polyamides. Specifically,6-aminocapronitrile can be used to produce nylon 6.

Aminonitriles can be produced by catalytic partial hydrogenation ofdinitriles. See, for example, U.S. Pat. No. 2,208,598, U.S. Pat. No.2,257,814, U.S. Pat. No. 2,762,835, U.S. Pat. No. 3,322,815, U.S. Pat.No. 3,350,439, U.S. Pat. No. 3,591,618, U.S. Pat. No. 4,389,348, U.S.Pat. No. 4,601,859, U.S. Pat. No. 5,151,543, U.S. Pat. No. 5,296,628,U.S. Pat. No. 5,512,697, U.S. Pat. No. 5,527,946, U.S. Pat. No.6,080,884, DE848654, DE-A-19636768 and WO99/47492 (corresponding to U.S.Pat. No. 6,080,884 and U.S. patent application Ser. No. 09/268,148,filed Mar. 15, 1999) all of which are incorporated by reference hereinfor all purposes as if fully set forth. However, the yield of andselectivity to a desired aminonitrile using some of the known processesmay not be as high as desired, and the amount of the completehydrogenation product (diamine) is also generally higher than desired.

WO99/47492 mentioned above describes the use of certain carbonylgroup-containing compounds as additives in the partial hydrogenationprocess to improve the yield of and/or selectivity to the desiredaminonitrile product, and/or reduce the amount of fully hydrogenatedproduct (diamine) produced.

We have now found new classes of compounds that also effectivelyfunction as improved yield and/or selectivity additives in the partialhydrogenation processes such as, for example, those mentioned inpreviously incorporated WO99/47492.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided a process for the partial hydrogenation of a dinitrile to anaminonitrile, comprising the step of contacting the dinitrile with ahydrogen-containing fluid in the presence of (a) a solvent comprisingliquid ammonia, an alcohol, or both; (b) a hydrogenation catalyst; and(c) an additive comprising a fluoride compound.

In accordance with another aspect of the present invention, there isprovided an improved process for preparing an aminonitrile from acorresponding dinitrile by contacting the dinitrile with ahydrogen-containing fluid in the presence of a solvent and ahydrogenation catalyst, wherein the improvement comprises contacting thedinitrile, hydrogen-containing fluid, solvent and hydrogenation catalystin the further presence of an additive comprising a fluoride compound.

Another aspect of the present invention relates to a method forimproving the yield of and/or selectivity to an aminonitrile obtained bypartially hydrogenating a corresponding dinitrile with ahydrogen-containing fluid in the presence of a solvent and ahydrogenation catalyst, comprising the step of partially hydrogenatingthe dinitrile in the further presence of an effective amount of anadditive comprising a fluoride compound.

In yet another aspect of the present invention, there is provided acatalyst composition comprising a combination of (1) a hydrogenationcatalyst suitable for partially hydrogenating a dinitrile to anaminonitrile; and (2) an additive comprising a fluoride compound.

An advantage of this invention is that an aminonitrile can be producedin higher yield and/or having a higher selectivity to the aminonitrilewith the fluoride additive than without. Other objects and advantageswill become more apparent as the invention is more fully disclosedherein below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to this invention, a dinitrile is contacted with ahydrogen-containing fluid in the presence of a solvent, a catalyst andthe fluoride additive.

Suitable dinitriles for use herein have the general formula R(CN)₂,wherein R is a hydrocarbylene group selected from the group consistingof an alkylene, arylene, alkenylene, alkarylene and aralkylene group.One dinitrile or combinations of different dinitriles may be used.Preferred hydrocarbylene groups contain from 2 to 25, more preferably 2to 15, and most preferably 2 to 10 carbon atoms per group. In otherwords, preferred dinitriles contain from 4 to 27, more preferably 4 toabout 17, and most preferably 4 to 12, carbon atoms per dinitrilemolecule. The preferred type of hydrocarbylene group is an alkylenegroup.

Examples of suitable dinitriles include, but are not limited to,adiponitrile; methylglutaronitrile; alpha,omega-butanedinitrile;alpha,omega-pentanedinitrile; alpha,omega-heptanedinitrile; alpha,omega-nonanedinitrile; alpha,omega-dodecanedinitrile;alpha,omega-pentadecanedinitrile; alpha,omega-icosanedinitrile;alpha,omega-tetracosanedinitrile; 3-methylhexanedinitrile;2-methyl-4-methyleneoctanedinitrile; and combinations of two or morethereof.

Preferably the carbon atoms of the starting dinitrile are arranged in abranched or linear chain. Preferred examples are adiponitrile(hydrogenated to 6-aminocapronitrile), methylglutaronitrile(hydrogenated to two isomeric aminonitriles:5-amino-2-methylvaleronitrile and 5-amino-4-methylvaleronitrile) andalpha,omega-dodecanedinitrile (hydrogenated to the correspondingaminonitrile). The preferred dinitrile is adiponitrile because itsselective hydrogenation product, 6-aminocapronitrile, is a well-knownmonomer for polymerization applications.

Any hydrogen-containing fluid can be used in the invention as long asthere is sufficient hydrogen in the fluid to selectively hydrogenate adinitrile to an aminonitrile. The term “fluid” refers to liquid, gas orboth. The hydrogen content in the fluid can range from 1 to 100%,preferably about 50 to about 100%, and most preferably 90 to 100% byvolume. The presently preferred hydrogen-containing fluid issubstantially pure hydrogen gas.

The molar ratio of hydrogen (in the hydrogen-containing fluid) todinitrile is not critical as long as sufficient hydrogen is present toproduce the desired aminonitrile. Hydrogen is generally used in excess.Hydrogen pressures are generally in the range of about 50 to about 2000psig (about 0.45 to about 13.89 MPa), with from about 200 to about 1000psig (about 1.48 to about 7.00 MPa) preferred.

Any solvent that comprises either liquid ammonia or an alcohol can beused in the invention. The concentration of liquid ammonia in thesolvent can range from about 20 to about 100%, preferably about 50 toabout 100%, and most preferably about 80% to about 100%, by weight oftotal solvent. A substantially pure liquid ammonia is preferred.However, if an alcohol is also present in the solvent, the concentrationof ammonia can be adjusted based on the quantity of alcohol used, whichis discussed in further detail below. The molar ratio of ammonia todinitrile is preferably about 1:1 or greater, and is generally in therange of from about 1:1 to about 30:1, more preferably from about 2:1 toabout 20:1.

Any alcohol that can facilitate the selected hydrogenation of adinitrile to an aminonitrile can be used in this invention. Preferredare alcohols with 1 to 10, more preferably 1 to 4, carbon atoms permolecule. Examples of suitable alcohols include, but are not limited to,methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutylalcohol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, andcombinations of two or more thereof. The most preferred alcohol (whenused) is methanol. The alcohol can generally be present in the solventin the concentration of from about 20 to about 100%, preferably about 30to about 99%, by weight based on the total solvent weight.

Typically when an alcohol is use, the solvent further comprises a basethat is substantially soluble in the solvent. The term “substantially”refers to “more than trivial”. Preferred bases are ammonia, an ammoniumbase or an inorganic base such as, for example, alkali metal oxides,alkaline earth metal oxides, alkali metal hydroxides, alkaline earthmetal hydroxides, partially neutralized acids in which one or moreprotons of the acids are replaced with ammonium ion, alkali metal ions,alkaline earth metal ions, or combinations of two or more thereof.Specific examples of suitable bases include, but are not limited toammonia, lithium hydroxide, sodium hydroxide, sodium oxide, potassiumhydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate,or combinations of two or more thereof. The most preferred bases areammonia, lithium hydroxide and sodium hydroxide for they are readilyavailable and inexpensive.

A base can be present in the solvent in any quantity so long as thequantity can facilitate the selective hydrogenation of a dinitrile to anaminonitrile. Generally, a base can be present in the solvent in therange of from about 1 to about 10 weight %, based on the total weight ofthe starting dinitrile.

The catalyst in the process is a hydrogenation catalyst suitable forpartially hydrogenating a dinitrile to an aminonitrile. Preferred arecatalysts based on transition metals selected from the group consistingof iron, cobalt, nickel, rhodium and combinations thereof. The catalystmay also contain one or more promoters, for example, one or more ofGroup VIB and Group VII metals such as chromium, molybdenum andtungsten. The catalyst can also be in the form of an alloy, anindividual metal or a solid solution of two or more metals.

The catalytic metal can also be supported on an inorganic support suchas alumina, magnesium oxide and combinations thereof. The metal can besupported on an inorganic support by any means known to one skilled inthe art such as, for example, impregnation, coprecipitation, ionexchange, and combinations of two or more thereof. The preferredinorganic support is magnesium oxide, and the preferred supportedcatalyst is a magnesium oxide supported nickel-iron catalyst.

The catalyst can be present in any appropriate physical shape or form.It can be in fluidizable forms, extrudates, tablets, spheres orcombinations of two or more thereof. The catalyst may be in sponge metalform, for example, the Raney® nickels and Raney® cobalts. The molarratio of catalyst to dinitrile can be any ratio as long as the ratio cancatalyze the selective hydrogenation of a dinitrile. The weight ratio ofcatalyst to dinitrile is generally in the range of from about 0.0001:1to about 1:1, preferably about 0.001:1 to about 0.5:1. If the catalyticmetal is supported on an inorganic support or is a portion of alloy orsolid solution, the catalytic metal is generally present in the range offrom about 0.1 to about 60, preferably about 1 to about 50, and mostpreferably about 2 to about 50 weight %, based on the total catalystweight.

The preferred catalyst is a sponge metal type catalyst. The metalliccomponent is iron, cobalt, nickel or combinations thereof. Commerciallyavailable catalysts of this type are promoted or unpromoted Raney® Ni orRaney® Co catalysts that can be obtained from the Grace Chemical Co.(Columbia, Md.), Activated Metals Corporation (Sevierville, Tenn.) orDegussa (Ridgefield Park, N.J.).

In the case of the preferred supported nickel/iron catalyst, the rate ofadiponitrile conversion increases with the amount of Ni deposited on thesupport. The preferred concentration of Ni is between about 5 and about50 weight %, and especially between about 25 and about 35 weight %,based on the catalyst weight (metals+support). The preferredconcentration of Fe is between about 0.2 and about 20 weight %, andespecially between about 0.5 and about 10 weight %, based on thecatalyst weight (metals+support).

Further details on the above components can be found from various of thepreviously incorporated references. Specific reference may be had, forexample, to U.S. Pat. No. 2,208,598, U.S. Pat. No. 2,257,814, U.S. Pat.No. 2,762,835, U.S. Pat. No. 3,322,815, U.S. Pat. No. 5,151,543, U.S.Pat. No. 5,296,628, U.S. Pat. No. 5,512,697, U.S. Pat. No. 5,527,946,U.S. Pat. No. 6,080,884 and WO99/47492.

A wide variety of fluoride compounds have been found that can effect theselectivity/yield improvement in the invention. The term “improvement”is referred to as enhanced selectivity to aminonitrile product atconversions greater than about 70%, preferably conversions greater thanabout 80%, as compared to the selectivity without the use of theadditive of this invention. An “effective amount” of the fluoridecompound is amount required to achieve the aforementioned enhancedselectivity and/or an improved overall yield of aminonitrile, ascompared to without the use of the fluoride compound.

Examples of suitable fluoride compounds include both organic andinorganic fluoride compounds such as, for example, tetramethylammoniumfluoride, tetraethylammonium fluoride, tetrapropylammonium fluoride,tetrabutylammonium fluoride, sodium fluoride, lithium fluoride,diisopropylethylamine trihydrofluoride, diisopropylaminedihydrofluoride, cerium titanium fluoride, hydrogen fluoride/melamine(80% HF), 1,3-dimethylimidazolidinone hexahydrofluoride,poly-4-vinylpyridinium poly(hydrogen fluoride), benzyltrimethylammoniumfluoride hydrate, antimony fluoride, potassium hexafluoronickelate(IV),potassium fluoride, triethylamine trihydrofluoride, tetraoctylammoniumfluoride, hydrogen fluoride, tetraethylammonium fluoride dihydrate,tetrabutylammonium fluoride trihydrate, hydrogen fluoride2,4,6-trimethylpyridine, pyridinium poly(hydrogen fluoride),tetramethylammonium fluoride tetrahydrate, hydrazinium difluoride,ammonium hexafluorophosphate fluoride, boron trifluoride-dipropionicacid complex and boron fluoride-acetic acid complex. Preferred of theabove are the amine and ammonium fluorides mentioned above as well asthe hydrates thereof.

The fluoride additive can be present during the contacting in anyquantity that can improve the selective hydrogenation of a dinitrile toits corresponding aminonitrile (e.g., an effective amount). Generally,the weight ratio of the additive to the catalyst is in the range of fromabout 0.001:1 to about 0.5:1, preferably about 0.01:1 to about 0.1:1.

The catalyst and fluoride additive can be separately introduced intocontacting with a dinitrile; however, it is preferred that the catalyst,whether it is in its metal form or in an alloy or solid solution or onan inorganic support, is precontacted with the additive. This may bedone in a solvent such as, for example, an alcohol, ether, ester,ammonia or combinations of two or more thereof. Further preferably theprecontacting is also carried out in a hydrogen-containing fluid such asdescribed above. Contacting of the catalyst and fluoride additiveproduces a pretreated catalyst. The pretreated catalyst can be washedwith a solvent disclosed above, preferably under anaerobic condition toproduce an additive-treated catalyst.

The contacting of the catalyst and fluoride additive can be carried outunder any conditions effective to produce an additive-treated catalystthat can improve selective hydrogenation of a dinitrile or theselectivity to an aminonitrile. Generally, the entire process forproducing the additive-treated catalyst can be carried out by contactinga catalyst with an additive disclosed above at a temperature in therange of from about 20° C. to about 150° C., preferably about 30° C. toabout 100° C., under the same general pressures as described above, forabout 5 seconds to about 25 hours.

The partial hydrogenation process of the present invention can becarried out at a temperature in the range of from about 25 to about 150°C., preferably about 40 to about 100° C., most preferably about 60 toabout 80° C., at a total pressure generally in the range of about 50 toabout 2000 psig (about 0.45 to about 13.89 MPa), with from about 200 toabout 1000 psig (about 1.48 to about 7.00 MPa) preferred, for a timeperiod generally in the range of from about 15 minutes to about 25hours, preferably about 1 hour to about 10 hours.

The process of the invention can be operated batch wise or continuouslyin an appropriate reactor. Stirring or agitation of the reaction mixturecan be accomplished in a variety of ways known to those skilled in theart. The partial hydrogenation of the starting dinitrile to itscorresponding aminonitrile with high selectivity at high conversions ofthe dinitrile makes this process efficient and useful.

Further general and specific process details can be found from variousof the previously incorporated references. Specific reference may behad, for example, to U.S. Pat. No. 2,208,598, U.S. Pat. No. 2,257,814,U.S. Pat. No. 2,762,835, U.S. Pat. No. 3,322,815, U.S. Pat. No.5,151,543, U.S. Pat. No. 5,296,628, U.S. Pat. No. 5,512,697, U.S. Pat.No. 5,527,946, U.S. Pat. No. 6,080,884 and WO99/47492.

The following examples further illustrate the process of the inventionand are not to be construed to unduly limit the scope of the invention.

The meaning of terms used in the Examples is defined as follows:

Yield of aminonitrile is the measured concentration of aminonitriledivided by the starting concentration of dinitrile.

Conversion of the dinitrile is the difference between the starting andthe instant concentration of dinitrile, divided by the startingconcentration of dinitrile.

Selectivity to aminonitrile is the measured yield of aminonitriledivided by conversion of the dinitrile at that instance.

COMPARATIVE EXAMPLE 1

Raney® Ni (1.2 g) promoted with Fe and Cr (Activated Metals, A4000,without any further additives) was added to a 50 cc autoclave togetherwith 3.2 g adiponitrile (ADN) and 35 cc of liquid ammonia to form amixture. Hydrogen was introduced to the autoclave and the ADN washydrogenated at 60° C. under the total pressure of 1045 psig (7.21 MPa),at ca. 1500 rpm). Total conversion of ADN was reached within 30 minuteson stream. The maximum yield of aminocapronitrile was 63% at 90% ADNconversion.

COMPARATIVE EXAMPLE 2

To a 300 cc autoclave, was charged 7.7 g Raney® Co (obtained from W.R.Grace Co.), 0.77 g water, 26 g ADN, and 139 g liquid ammonia. Thecontent was hydrogenated at 70° C., under the total pressure of 1000psig (7.00 MPa), at 1000 rpm. Total conversion of ADN was reached within40 minutes on stream. The maximum yield of aminocapronitrile was ca. 64%at 90% ADN conversion.

COMPARATIVE EXAMPLE 3

1.2 g of Rh(5%) on Al₂O₃ (Engelhard) was added to a 50 cc autoclavetogether with 3.2 g adiponitrile (ADN) and 35 cc of liquid ammonia.Hydrogen was introduced to the autoclave and the ADN was hydrogenated at80° C. under the total pressure of 1060 psig (7.31 MPa) at ca. 1500 rpm.Total conversion of ADN was reached within 30 minutes on stream. Themaximum yield of aminocapronitrile reached 35% at 40% ADN conversion.

EXAMPLE 1

1.2 g Raney® Ni was charged into a 50 cc autoclave, together with 0.5 gof tetraethylammonium fluoride hydrate. Subsequently 35 cc of liquidammonia was added, and the mixture was heated to 80° C. with stirring;the pressure was adjusted to 1000 psig (7.00 MPa) with hydrogen, thenkept under such conditions for 1.0 hrs. After cooling, the liquid phasewas filtered off, leaving the pretreated catalyst inside of theautoclave. 3.2 g of ADN was injected into the autoclave and 35 ml ofliquid ammonia was added, the mixture was heated to 70° C., and reactedwith hydrogen at a total pressure of 1000 psig (7.00 MPa). The yield of6-aminocapronitrile reached 83% after 45 min. The conversion of ADN was96% at this point.

EXAMPLE 2

1.2 g Raney® Ni and 3.2 g of ADN were charged into a 50 cc autoclave,together with 0.3 g of tetraethylammonium fluoride hydrate. Subsequently35 cc of liquid ammonia was added, and the mixture was heated to 80° C.with stirring and reacted with hydrogen at a total pressure of 1044 psig(7.30 MPa). The yield of 6-aminocapronitrile reached 79% after 20 min.The conversion of ADN was 98% at this point.

EXAMPLE 3

1.2 g Raney® Ni was charged into a 50 cc autoclave, together with 1.0 gof tetraethylammonium fluoride hydrate. Subsequently 35 cc of liquidammonia was added, and the mixture was heated to 80° C. with stirring;the pressure was adjusted to 1000 psig (7.00 MPa) with hydrogen, thenkept under such conditions for 1.0 hrs. After cooling, the liquid phasewas filtered off, leaving the pretreated catalyst inside of theautoclave. 3.2 g of ADN was injected into the autoclave and 35 ml ofliquid ammonia was added, the mixture was heated to 70° C., and reactedwith hydrogen at a total pressure of 1047 psi (7.32 MPa). The yield of6-aminocapronitrile reached 83% after 55 min. The conversion of ADN was97% at this point.

EXAMPLE 4

1.2 g Raney® Co was charged into a 50 cc autoclave, together with 2.0 gof tetraethylammonium fluoride hydrate. Subsequently 35 cc of liquidammonia was added, and the mixture was heated to 80° C. with stirring;the pressure was adjusted to 1000 psig (7.00 MPa) with hydrogen, thenkept under such conditions for 1.0 hrs. After cooling, the liquid phasewas filtered off, leaving the pretreated catalyst inside of theautoclave. 3.2 g of ADN was injected into the autoclave and 35 ml ofliquid ammonia was added, the mixture was heated to 70° C., and reactedwith hydrogen at a total pressure of 1000 psig (7.00 MPa). The yield of6-aminocapronitrile reached 74% after 16 min. The conversion of ADN was94% at this point.

EXAMPLE 5

1.2 g Rh(5%)/Al₂O₃ was charged into a 50 cc autoclave, together with 0.5g of tetraethylammonium fluoride hydrate. Subsequently 35 cc of liquidammonia was added, and the mixture was heated to 80° C. with stirring;the pressure was adjusted to 1000 psig (7.00 MPa) with hydrogen, thenkept under such conditions for 1.0 hrs. After cooling, the liquid phasewas filtered off, leaving the pretreated catalyst inside of theautoclave. 3.2 g of ADN was injected into the autoclave and 35 ml ofliquid ammonia was added, the mixture was heated to 70° C., and reactedwith hydrogen at a total pressure of 1000 psig (7.00 MPa). The yield of6-aminocapronitrile reached 76% after 40 min. The conversion of ADN was94% at this point.

I claim:
 1. A catalyst composition comprising a combination of (1) ahydrogenation catalyst suitable for partially hydrogenating a dinitrileto an aminonitrile, the hydrogenation catalyst being selected from thegroup consisting of sponge metal cobalt, sponge metal nickel, asupported nickel-iron catalyst and a supported rhodium catalyst; and (2)an additive comprising a fluoride compound.
 2. The catalyst compositionof claim 1, wherein the hydrogenation catalyst is pretreated with theadditive.
 3. The catalyst composition of claim 2, wherein thehydrogenation catalyst is sponge metal nickel or sponge metal cobalt. 4.The catalyst composition of claim 3, wherein the additive comprises afluoride compound selected from the group consisting of amine fluorides,ammonium fluorides and the hydrates thereof; and the weight ratio ofadditive to hydrogenation catalyst is in the range of from about 0.001:1to about 0.5:1.
 5. The catalyst composition of claim 2, wherein thehydrogenation catalyst is a supported nickel/iron catalyst or asupported rhodium catalyst.
 6. The catalyst composition of claim 5,wherein the additive comprises a fluoride compound selected from thegroup consisting of amine fluorides, ammonium fluorides and the hydratesthereof; and the weight ratio of additive to hydrogenation catalyst isin the range of from about 0.001:1 to about 0.5:1.
 7. The catalystcomposition of claim 2, wherein the fluoride compound is selected fromthe group consisting of amine fluorides, ammonium fluorides and thehydrates thereof.
 8. The catalyst composition of claim 2, wherein theweight ratio of additive to hydrogenation catalyst is in the range offrom about 0.001:1 to about 0.5:1.
 9. The catalyst composition of claim2, wherein the additive comprises a fluoride compound selected from thegroup consisting of amine fluorides, ammonium fluorides and the hydratesthereof; and the weight ratio of additive to hydrogenation catalyst isin the range of from about 0.001:1 to about 0.5:1.
 10. The catalystcomposition of claim 1, wherein the catalyst further comprises one ormore promoters selected from the group consisting of Group VIB and GroupVII metals.
 11. The catalyst composition of claim 1, wherein thehydrogenation catalyst is sponge metal nickel or sponge metal cobalt.12. The catalyst composition of claim 11, wherein the additive comprisesa fluoride compound selected from the group consisting of aminefluorides, ammonium fluorides and the hydrates thereof; and the weightratio of additive to hydrogenation catalyst is in the range of fromabout 0.001:1 to about 0.5:1.
 13. The catalyst composition of claim 1,wherein the hydrogenation catalyst is a supported nickel/iron catalystor a supported rhodium catalyst.
 14. The catalyst composition of claim13, wherein the additive comprises a fluoride compound selected from thegroup consisting of amine fluorides, ammonium fluorides and the hydratesthereof; and the weight ratio of additive to hydrogenation catalyst isin the range of from about 0.001:1 to about 0.5:1.
 15. The catalystcomposition of claim 1, wherein the fluoride compound is selected fromthe group consisting of amine fluorides, ammonium fluorides and thehydrates thereof.
 16. The catalyst composition of claim 1, wherein theweight ratio of additive to hydrogenation catalyst is in the range offrom about 0.001:1 to about 0.5:1.
 17. The catalyst composition of claim1, wherein the additive comprises a fluoride compound selected from thegroup consisting of amine fluorides, ammonium fluorides and the hydratesthereof; and the weight ratio of additive to hydrogenation catalyst isin the range of from about 0.001:1 to about 0.5:1.